Ink-jet recording apparatus which form an image by discharging an ink which is set when receiving the energy of ultraviolet light or an electron beam toward a recording medium using an ink-jet head and then applying energy to the ink have various features; for example, they are environment-friendly, can perform high-sped recording on various recording media, and can produce high-resolution images because the ink is less prone to soak into recording media.
In particular, the development of apparatus using an ultraviolet-setting ink is making rapid progress because of case of handling of a light source, compactness, etc. And what is called a single-pass ink-jet recording apparatus in which a web-like recording medium capable of being transported at high speed is used, a fixed head wide enough to perform recording over the full width of a recording medium is opposed to the recording medium, and recording is completed by only one pass of the recording medium under the head has been invented by taking advantage of high-speed fixing performance of the ultraviolet-setting ink.
When color printing is performed with such a single-pass ink-jet recording apparatus, fixed heads are arranged in the number of colors in the transport direction of a recording medium. To prevent mixing of inks of different colors, JP-A-2004-314586 discloses an apparatus in which a light illumination means is disposed downstream of the head of each color.
JP-A-2004-237602 discloses an ink-jet recording system using cation-type ultraviolet-setting inks and inexpensive cold cathode fluorescent tubes or hot cathode fluorescent tubes.
FIG. 6 shows a single-pass ink-jet recording apparatus disclosed in JP-A-2004-314586. In FIG. 6, reference numeral 60 denotes a conventional single-pass ink-jet recording apparatus. In the single-pass ink-jet recording apparatus 60, a recording medium S is pulled out of a recording medium roll 61 which is a roll-wound recording medium. First, a desired image of a Y (yellow)-color ultraviolet-setting ink is recorded on the recording medium S as it is transported under a Y-color full-line ink-jet head 63Y in which a large number of ink-jet nozzles are arranged in the width direction (i.e., in the direction perpendicular to the paper surface of FIG. 6) of the recording medium S. Immediately thereafter, the Y-color ink that has been discharged and placed on the recording medium S is fixed receiving an active energy ray as the recording medium S passes under an active-energy-ray-setting lamp 64. High light intensity is necessary for setting of the ink, and a very expensive high-pressure mercury lamp, medium-pressure mercury lamp, or metal halide lamp is used as the light source.
Then, a desired image of an M (magenta)-color ultraviolet-setting ink is recorded on the recording medium S as it is transported under an M-color full-line ink-jet head 63M in which a large number of ink-jet nozzles are arranged in the width direction of the recording medium S. Immediately thereafter, the M-color ink that has been discharged and placed on the recording medium S is fixed receiving an active energy ray as the recording medium S passes under another active-energy-ray-setting lamp 64.
Then, a desired image of a C (cyan)-color ultraviolet-setting ink is recorded on the recording medium S as it is transported under a C-color full-line ink-jet head 63C in which a large number of ink-jet nozzles are arranged in the width direction of the recording medium S. Immediately thereafter, the C-color ink that has been discharged and placed on the recording medium S is fixed receiving an active energy ray as the recording medium S passes under another active-energy-ray-setting lamp 64.
Finally, a desired image of a B (black)-color ultraviolet-setting ink is recorded on the recording medium S as it is transported under a B-color full-line ink-jet head 63B in which a large number of ink-jet nozzles are arranged in the width direction of the recording medium S. Immediately thereafter, the B-color ink that has been discharged and placed on the recording medium S is fixed receiving an active energy ray as the recording medium S passes under a metal halide lamp 65 which is higher in light intensity than the above-mentioned active-energy-ray-setting lamps 64. Four-color-ink recording is thus performed.
As described above, because of a superior high-speed fixing characteristic, ultraviolet-setting inks are applied to the above-described single-pass ink-jet recording apparatus. And several systems are now on the market which are advantageous in that, for example, they are high in productivity, enable image drawing on various recording media, and are environment-friendly.
On the other hand, high light intensity is necessary for setting inks, and a very expensive high-pressure mercury lamp, medium-pressure mercury lamp, metal halide lamp, or the like is used as each ink-setting light source.
FIG. 7 shows an ink-jet recording apparatus disclosed in JP-A-2004-237602 which uses inexpensive hot cathode fluorescent tubes. In FIG. 7, reference numeral 70 denotes a single-pass ink-jet recording apparatus; 71, a transport belt, 73, ink-jet heads (73Y: yellow head, 73M: magenta head, 73C: cyan head, 73B: black head); 74, inexpensive hot cathode fluorescent tubes; and 75, a light source which is higher in power than the hot cathode fluorescent tubes 74 and provides sufficient light intensity to set inks.
The invention of JP-A-2004-314586 has the following problems. That is, in the case of a high-productivity apparatus, the ultraviolet light illumination unit is expensive because the illumination light intensity needs to be increased to compensate for short illumination periods. To prevent mixing of inks, the apparatus become very costly. On the other hand, the invention of JP-A-2004-237602 has a problem that the setting characteristic is insufficient particularly under a high-speed condition because of low light intensity of the hot cathode fluorescent tubes.